NEET Solved Paper 2014 Question 39
Question: When the energy of the incident radiation is increased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. ‘The work function of the metal is [AIPMT 2014]
Options:
A) 0.65 eV
B) 1.0 eV
C) 1.3 eV
D) 1.5 eV
Show Answer
Answer:
Correct Answer: B
Solution:
For photo electric equation $ {{(KE)} _{\max }}=hv-{\phi_0} $ For the first condition $ 0.5=E-{\phi_0} $ ..(i)
For the second condition $ 0.8-1.2E-{\phi_0} $ ..(ii)
From Eqs. (i) and (ii) $ 0.5=E-{\phi_0} $ and $ 0.8=1.2E-{\phi_0} $ $ -0.3=-0.2E $ $ E=\frac{0.3}{0.2}1.5eV $
From expression (i) $ 0.5=1.5-{\phi_0}\Rightarrow {\phi_0}=0.5-0.5=1eV $
